Taewook Oh 956f97e693 [MergeICmps] Do not perform the transformation if GEP is used outside of block ...

Summary:
This patch prevents MergeICmps to performn the transformation if the address operand GEP of the load instruction has a use outside of the load's parent block. Without this patch, compiler crashes with the given test case because the use of `%first.i` is still around when the basic block is erased from https://github.com/llvm-mirror/llvm/blob/master/lib/Transforms/Scalar/MergeICmps.cpp#L620. I think checking `isUsedOutsideOfBlock` with `GEP` is the original intention of the code, as the checking for `LoadI` is already performed in the same function.

This patch is incomplete though, as this makes the pass overly conservative and fails the test `tuple-four-int8.ll`. I believe what needs to be done is checking if GEP has a use outside of block that is not the part of "Comparisons" chain. Submit the patch as of now to prevent compiler crash.

Reviewers: courbet, trentxintong

Reviewed By: courbet

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D54089

llvm-svn: 346151

2018-11-05 18:16:32 +00:00

..

X86

[MergeICmps] Do not perform the transformation if GEP is used outside of block

2018-11-05 18:16:32 +00:00

pair-int32-int32.ll

Re-land "[MergeICmps] Disable mergeicmps if the target does not want to handle memcmp expansion."

2017-10-10 08:00:45 +00:00